Proton therapy is a highly targeted form of radiation therapy, which means that doctors are better able to guide where the radiation goes in a patient's body. It also lowers the chances of damaging surrounding tissues and organs, which is highly important for a cancer like mesothelioma that often occurs near the lungs and heart.
Proton Therapy Explained
When a patient receives traditional radiation therapy for mesothelioma, both sides of a person’s body are hit with the radiation. However, in proton therapy, the healthy lung is not touched. Or if it is hit with radiation, it’s only a small amount because the doctor guides the protons. Having control over the protons keeps the majority of the radiation isolated to one side of the body.
A newer version of proton therapy called pencil-beam scanning (PBS) was pioneered at the MD Anderson Proton Therapy Center.
PBS proton therapy uses steering magnets to paint proton beam spots layer-by-layer over the target area. Before PBS, proton therapy required a custom-made scattering device that was used to mold the beam into the shape of the lungs and diaphragm or whatever area of the body the radiation oncologist was trying to treat.
PBS Proton Therapy Reduces Damage to Nearby Tissues
Because PBS proton therapy no longer requires custom equipment, the treatment team can give the patient intensity-modulated proton therapy (IMPT)—when the doctor uses a higher therapeutic dose of radiation—without having to worry about causing unnecessary damage to surrounding tissues and organs.
How Proton Therapy Works
In proton therapy, a proton—a positively charged part of an atom—is shot from a proton accelerator through the patient’s body. As the accelerator speeds up the proton, the proton’s energy levels also increase to a total of somewhere between 70 million and 250 million electron volts. The volt level will vary depending on how deep into the body the proton needs to go.
The proton beams are shaped to the precise shape and depth of the tumor using a complex system of magnets. Once the proton has reached the correct spot, it will release its excess energy and kill the surrounding cells.
Proton Therapy for Mesothelioma
Traditionally, there are 3 times radiation therapy is used to help pleural mesothelioma patients:
- Palliative Therapy: Research has shown patients who receive radiation therapy as a palliative treatment experience relief from their symptoms and have a lower level of pain.
- Adjuvant Therapy: It is also used after a patient had an extrapleural pneumonectomy (EPP) to help kill off any cancer cells that may have been left behind when the lung was removed. But this form of radiation can damage the other lung and increase the risk of fatal pneumonitis.
- Preventive Therapy: Radiation is used as a preventive measure around biopsy or drain sites to prevent seeding—when cancer cells travel along the track left by the needle and form a new tumor where they land. While studies don’t agree whether or not seeding is likely to happen during a biopsy or fluid drain, many doctors offer radiation therapy at the track sites to be safe because a new tumor can be deadly.
Mesothelioma Treated With Proton Therapy
The most common type of mesothelioma that can be treated with proton therapy is stage 3 or 4 pleural mesothelioma with epithelioid cell type. However, proton therapy can be used for other cells types as well.
With the introduction of proton therapy, radiation treatment can now be used in the following scenarios for treating mesothelioma:
- To help shrink the tumor before a patient undergoes pleurectomy with decortication (P/D), after a P/D or EPP to deal with the surviving cancer cells the operation left behind.
- As a stand-alone treatment for patients who cannot have surgery to remove the tumor.
Benefits of Proton Therapy for Mesothelioma
There are many benefits to proton therapy for mesothelioma:
- IMPT or traditional proton therapy both have a lower risk of giving the patient radiation pneumonitis.
- Physicians are better able to plan where the proton will release the majority of its energy to cause the most damage to tumor cells while preventing harm from the surrounding tissue and organs.
- The treatment teams can use a higher dose of radiation because they can deliver it exactly where it needs to be.
- Patients report fewer side effects, and the side effects that do occur tend to end quickly.
- Proton radiation has a short life, which means patients don’t have to worry about exposing others to radiation once they’ve left the treatment room.
- Patients can continue to work and exercise while they are undergoing proton therapy.
Side Effects of Proton Therapy for Mesothelioma
As with any form of treatment for mesothelioma, proton therapy is not without side effects. Some of the common side effects are:
- A cough
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Latest Research in Proton Therapy for Mesothelioma
In a study that was in Cureus, a research team looked at 3 case studies of different men who were treated with proton therapy for mesothelioma.
In the first case study, a 71-year-old man with stage 3 biphasic (mixed) pleural mesothelioma had IMPT after an EPP. Four months later, he was struggling to breathe when he was exerting himself, and follow-up tests showed that the cancer had started growing in his nodules in his opposite lung. However, he survived for 25 months after the proton therapy radiation treatment.
The second case study the team looked at was that of a 47-year-old man with stage 4 epithelioid mesothelioma. Unfortunately, during his EPP the surgeons discovered that the cancer had spread further than they had expected. Even with the proton therapy it regrew quickly, and he passed away four months after receiving the radiation treatment.
Finally, they looked at a 46-year-old man with stage 3 epithelioid mesothelioma. He received IMPT after he had an EPP and chemotherapy. At the time of publication, he was still doing well, and it had been 14 months since he received the radiation therapy.
Undergoing Proton Therapy for Mesothelioma
Patients who are interested in proton therapy should get in touch with a mesothelioma specialist or radiation oncologist to treat their mesothelioma.
Some places where patients can go to receive proton therapy are The University of Texas MD Anderson Cancer Center or The University of Maryland Marlene and Stewart Greenbaum Comprehensive Cancer Center.
For more information on radiation therapy for mesothelioma, contact our Patient Advocates today. Call us at (800) 584-4151 and receive a FREE Mesothelioma Help Guide to better understand your peritoneal mesothelioma treatment options.